Shaped by Fire: Unravelling the Impact of Fire on Lizard Gut Microbiome

Abstract

In recent decades, wildfire regimes have changed significantly, with increases in frequency, severity and area affected, leading to major habitat alterations that may impact species ecology. While fire's role in plant ecology is well studied, its effects on animal biotic interactions remain poorly understood. In northern Portugal, where wildfires are common, the native rock-dwelling lizard Podarcis lusitanicus may thrive postfire due to its preference for open rocky outcrops, which expand after fires. This suggests not only resilience but also a capacity for persistence in postfire disturbances driven by habitat preferences. However, changes in prey availability after fire induce dietary shifts in this insectivorous lizard, potentially affecting trophic interactions and, consequently, gut microbiota communities. Gut microbiota influence host fitness through effects on nutrition, immunity and behaviour; on the other hand, gut microbiota are affected by variations in diet and environment. This study assessed how fire history affects P. lusitanicus gut microbiota. Sampling occurred across 12 sites in northern Portugal, representing three fire histories: long-unburned, burned in 2016 and burned in 2022. Cloacal swabs were analysed by metabarcoding the V4 region of the 16S rRNA gene. Results showed that gut bacterial composition varied with fire history, as well as with sex, body size and diet. Females had higher microbial richness despite similar diet richness between sexes. While microbiome composition shifted, predicted microbiome function remained relatively stable, indicating both resilience and ecological flexibility in fire-prone environments. These findings enhance understanding of how lizard microbiomes respond to environmental disturbances and may help predict host and microbiota tolerance under changing fire regimes.

Keywords: Podarcis; Portugal; fire ecology; gut microbiota; metabarcoding.

FIGURE 1

Maps of the different sampling sites: Viana do Castelo (VC), Álvora (AL), Gerês‐Soajo (GS) and Marco de Canaveses (MC)—with three capture sites selected across different historic fire conditions: Burned in 2016 (in yellow), burned in 2022 (in blue) and the long‐unburned site. Map data 2024 Google.

FIGURE 2

Photographs of the three different capture sites in Álvora (AL): A—area burned in 2016; B—area burned in 2022; C—long‐unburned área, and a representative male individual of P. lusitanicus.

FIGURE 3

Boxplots showing alpha diversity metrics across localities in P. lusitanicus . (A) Faith's Phylogenetic Diversity (PD) and (B) ASV Richness are displayed by sex (Female and Male). Points represent individual samples to highlight data distribution within each sex category.

FIGURE 4

Canonical Analysis of Principal Coordinates (CAP) ordinations of gut microbiome composition based on unweighted UniFrac dissimilarity. Points represent individual samples, coloured by fire history (Fire_regime) and shaped by sex. Ellipses indicate 95% confidence intervals for each fire history group. Title show the proportion of variance (R ²) explained by the constrained model (Type_fire, Sex, SVL).

FIGURE 5

Differential abundance analysis of microbial taxa. The left panel represents significant changes at the genus level, while the right panel shows changes at the phylum level, comparing microbial communities between fire regimes in 2016 and 2022. Coloured error bars indicate significant differences, with red representing a decrease and blue representing an increase in relative abundance.